Process of improving lubricating oil



July 28, 1936.

A. M. M AFEE ET AL PROCESS OF IMPROVING LUBRICATING O IL Filed March 21, 1934 LUBRICA TING STOCK ALUMINUM lcoNTAcT CLAY s CHLORIDE TREATING VESSEL A-M-M AFEE L-O-CfQOCKETT [NVENTORS W A TTORNEY Patented July 28, 1936 UNITED STATES PROCESS or nurnovmc nnnnrcs'rnvc on.

Almer M. McAfee and Lucien 0. Crockett, Port Arthur, Tex., assignors, by mesne assignments, to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania.

Application March 21, 1934, Serial No. 716,732

2 Claim.

This invention relates to process of improving lubricating oil; and it comprises a method in which lubricating stock is agitated for several hours with anhydrous aluminum chlorid at a temperature approaching but below that at which extensive production of lower boiling oils occurs, the temperature of treatment ranging between 300 F. and 475 F., and finishing the so treated oil by customary refining methods; all as more fully hereinafter set forth and claimed.

The most important characteristic of lubricating oil is viscosity, and the ideal lubricating oil would be one having substantially the same viscosity at all temperatures to which it is subjected in use. Such an ideal lubricating oil has never been produced from crude petroleum, and all known petroleum lubricating oils become less viscous as their. temperature increases. Oils from some crudes sufier less change of viscosity with change of temperature than do oils from other crudes. It is well known, for example, that oils made from paraffinictype crudes undergo less change of viscosity with change of temperature than do oils made from naphthenic type crudes; it is also well known that the viscosity of oils made from the paraflin base crude of Pennsylvania undergo less change of viscosity with change of temperature'than do oils made from paraffin base mid-continent crude. Similarly, lubricating oils made from paraifin base mid-continent crude are better in this respect than lubricating oils made from Texas coastal crude. This relation of viscosity to temperature is now usually measured and expressed in terms of viscosity index, which latter is described by Dean and Davis in Chemical ,and, Metallurgical Engineering volume 36, page 618.

The object of this invention is improvement of lubricating oils, with particular respect to their viscosity indexes.

We find that by comparatively inexpensive treatment we can alter the viscosity index of various lubricating oils, that from Texas coastal crude we can produce a lubricating oil having such a. viscosity index as is ordinarily, found in lubricating oils produced from mid-continent crude, that from mid-continent stock we canproduce an oil having a viscosity index such as that which characterizes lubricating oils F. At higher made from Pennsylvania crude, and that from Pennsylvania crude we can produce oils which are properly characterized as Super-Pennsylvania in every respect. In each of these cases it will be noted that by our process wecproduce 5 lubricating oils characterized by viscosity indexes ordinarily characteristic ofShighergrade stock than that which we use.

In our process, a lubricating stock is heated for some time with a small amount of anhydrous aluminum chlorid: .the mass is stirred during this treatment; and the treatment is conducted advantageously at a temperature of about 425 temperatures, such as 600 F., a considerable proportion of the oil charged will be converted into products of lower boiling point and lower viscosity than the material operated on, and the viscosity index of the oil will be lowered instead of raised. Temperatures very materially below 425 F., say below 300 F., do not eflfect the desired alteration in the characteristics of the oil being treated. We find that a temperature of about475 F. is as high as can be used for our purpose. The amount of aluminum chlorid necessary for the conduct of our process varies with the oils being treated, but ordinarily no more than 10% by weight is required with any oil. This treatment with aluminum chlorid at elevated temperature may be effected by putting all of the aluminum chlorid on the oil in one treatment, or the oil may be subjected to only a portion of the aluminum chlorid in one treatment, sludge from such treatment is then removed from theoil and partially treated oil is then subjected to further treatment with the remainder of the aluminum chlorid. This latter mode of treatmerit we refer to as two-stage" treatment. In all cases the sludge is settled and separated from the oil prior to further processing. After the aluminum chlorid treatment, whether it be single stage or two-stage treatment, we charge the treated oil into a reducing still and there reduce it to the desired viscosity. We preferably use contact clay in the reducing still during the reducing operation, and we find one-halfpound of clay per gallon of oil a suitable proportion.

When the term flubricating stock is used herein, it is used in the mode most common in the petroleum refining industry; that is, either 0 for a petroleum fraction characterized by such viscosity and fire test that it will produce a finished commercial lubricating oil when refined by conventional sulfuric acid treatment orby filtration through clay or other equivalent refining process for removing asphaltic components therefrom and improvingthe color and carbon residue test thereof, or for a petroleum fraction composed }predominantly of such a material together with a minor portion of related material of adjacent boiling range which is incidentally present and which minor portion will be removed by distillation in the finishing steps. As used here. the term excludes all materials other than liquid petroleum the predominant portion of which is characterized by viscosity suitable for lubricating purposes, and it specifiamples of the practice of our invention, and,

these specific examples include treatment of lubricating distillates from Texas coastal crude,

and treatment of unfiltered bright stocks frommid-continent crudes, from a West Texas crude, and from a Pennsylvania crude.

The accompanying flow, chart graphically presents our process. Referring to the flow chart, Fig. 1, reference number one represents a tank of the material with which we start. This is 'a lubricating stock, and is ordinarily a dewaxed or wax-free stock. The stock from tank number one is charged into treating vessel 2,

which vessel is provided with an agitating device .3 driven by.a motor 4, and the stock is there treated at temperatures of approximately 300 F. to 475 F., with anhydrous aluminum I chlorid. Sludge from this treatment issettled out, isseparately withdrawn from treating vessel 2, and is discharged from the process at 5.

. After sludge has been settled out, the treated 'oil is separately withdrawn from vessel 2 through line 6. Contact clay, ordinarily in the proportion of approximately one-half pound of clay per gallon of treated oil is introduced into the treated oil-at I. The treated oil, together with the added clay, is then passed through a heating coil 8 in furnace 9, and from there it goes to flash tower Ill. The heating coll i and flash tower l8 comprise a reducing still, and the treated oil is there reduced to the desired viscosity. Steam is introduced into the-oil during this distillation. Material distilled off during the reducing distillation is condensed in condenser II, and it then leaves the process. Thereduced treated oil leaves the reducing still through line I2, is then passed through a filter or other means [3 for removal of contained clay, and then leaves the process throughline ll as the final product of our process. The aluminum chlorid'used in the treatment is fed to treating vessel 2 from a source of supply is. specific examples hereinafter set forth, the lubricating stock fed to our-process, if from Pennsylvania crude, has been dewaxed; if from a wax-bearing crude which also contains a substantial' amount of asphaltic constituents, it has In the' been acid treated and dewaxed; if from anonwax-bearing crude, the stock [is charged to our process direct from the still. As a refining procedure. we prefer, if a lubricating stock requires dewaxing, that the stock be dewaxed prior to our herein disclosed process, but the prior removal of wax is dictated solely by ordinary refining considerations. Acid treatment prior to dewaxing is not essential, but merely permits more complete removal of the contained wax than would otherwise be possible at the dewaxing temperature used. We wish to emphasize that our process is an eflicacious and valuable one regardless of whether the wax is removed before or after our herein disclosed treatment. A lubricating oil distillate from Texas coastal crude (the latter being a naphthenic type crude) was treated with 98% sulphuric acid in the amount of 30 pounds of acid per barrel of oil, this being 9.2% of acid by weight. The treated oil was then washed with caustic soda and blown bright. Following are the tests on the oil before and after finishing:

Table I Lubricating Treated oil distillate lubricating oil Acid treatment (98% sulfuric):

Pounds acid used, per bbl 30 Acid used, percent by-weight 9. 2 Treating temperature F tl'ield of finished nil 82 Gravity, A. P I 20. 6 21.9 viscosity, 8. U

At 100 F 980 843 At 210 F" 67 65 Viscosity index 15 29 Flash, F 410 420 Fire, F 470 480 Pour, 0 0 Color, N. P. A.....' 2 5 dil. 3 Carbon residue percent 0. 0. 17

The above treatment represents the usual practice in finishing this type of oil for the market. It will be observed that there has been only a slight improvement in the viscosity index' and slight rise in the gravity and flash and fire tests. The carbon residue test remained practically the same.

A lubricating oil distillate from Texas coastal crude (the latter being a naphthenic type crude) was treated with 98% sulphuric acid in the amount of :12 pounds of acid per barrel of oil, this being 13% of acid by weight. The'so treated oil was then charged to a reducing still together with contact clay in the amount of /2 pound per gallonof sour oil. The oil was then reduced with fire and bottom steam to a viscosity of '15 at 210 F.

Another lot of the same lubricating oil distillate was treated with anhydrous aluminum chlorid instead of sulfuric acid. The amount of chlorid used was 32.5 pounds per barrel of oil, this being 10% by weight. The treat was made in two stages. In the-first stage, 4% by weight of aluminum chlorid was added to the distillate and this was stirred for 4 hours at a temperature of 425? F. Sludge resulting from the treatment was allowed to settle and was removed from the supernatant oil. In the second stage, the remaining portion of aluminum chlorid (6%) was added to the oil from the first stage treatment and this was then stirred for 4 hours at a temperature of 307 F. Sludge was allowed to settle and was removed from the oil. The so treated oil was charged to a reducing still together with contact clay in the amount of /2 pound per gallon of oil. The oil was then reduced with fire and bottom steam .to a viscosity of 72 at 210 F.

The following table of figures gives details of the treatments and compares the product of the sulphuric acid treatment with the product of the aluminum chlorid treatment: 1

Table II Lubricating Lubricating Lubricating oil distillate oil oil distillate aluminum distillate acid treated chlorid v treated Acid treatment (98% sulfuric):

Acid used, lbs. per bbl Acid used, percent by weight Treating tcmperature, F. 121-129 Aluminum chlorid treat ment: Firststagei Chlorid used, lbs. per

bb1 l3 Chlorid used, percent by weight 4 Treating temperature, F 425 Time of tree hours 4 Second stage- Chlorid used, lbs. per bbl 19. 5 Chlorid used, percent by weight 6 Treating tempe ture, F 307 Time of treating,

hours 4 Yield of treated oil. percent.-. B9. 8 79. 1 Contact clay used, lbs. per 7 gall 0.5 0. 5 Temperature otreduct n. F. 500 500 Distillate from reducing still,

percent 7. 33.5 Yield of reduced oil, pement" 79. 3 42. 9 Tests:

Gravity, A. P. I 20. 5 22. 1 24.8 Viscosity, S. U. V

100 F 1227 1204 894 210 F 73 75 72 Viscosity index l3 19 60 Flash, C. O. C 425 435 455 Fire, C. O. 0., F 500 520 540 our, F 5 5 Color, N P. A 3 dil. 2. 25 2.75 Carbon residue, percent.-- 0. 23 0. l4 0. 09

It will be observed that the amount of sulfuric acid used in the first of the examples in Table II was much greater than the amount of aluminum chlorid used in the second example. But, while treatment with 13% by weight of sulfuric acid raised the viscosity index of the oil only from 13 to 19, it will be seen that treatment with only 10% of aluminum chlorid effected an improvement in viscosity index from 13 to 60. A viscosity index of 60 is such as ordinarily characterizes a mid-continent paraffin type oil rather than a naphthenic type-Texas coastal oil, which latter is the material used in the examples reported in Table II. It will also be observed that the aluminum chlorid treatment produces an oil of con-1 siderably lighter gravity and higher flash and fire tests. In general, our experience has been that for the same viscosity at 210 F. of a given oil, improvement of viscosity index is always accompanied by lighter gravity and higher flash and fire tests. This relationship does not hold in respect to the carbon residue test. As will be shown subsequently, it is possible to improve the viscosity index without lowering the carbon residue. In fact, we have seen examples where the carbon residue has actually increased with improved viscosity index. In the above example, it will be noted that the carbon residue test was lowered from 0.23% to 0.09%.

A lubricating oil distillate from Texas coastal crude (the latter being a naphthenic type crude) was treated with aluminum chlorid in the amount of 13 pounds per'barrel of oil, this being 4% by weight. The treating was done at 470 F., while stirring, and was continued 12 hours. Sludge resulting from the treatment was allowed tle.out and the treated oil was then charged to a reducing still together with contact clay in the amount of pound per gallon of oil. The oil was then reduced with aid of fire and bottom steam to a viscosity of '75 at 210 F.

Another lot of the same oil was treated in two stages with aluminum chlorid, the first stage being for 12 hours at 470! F. while stirring with 4% of chlorid. The sludge resulting from the treatment wasallowed to settle and the supernatant oil was given a second stage treatment with 6% aluminum chlorid at 307" F. for 12 hours. treated gether oil was charged to a'reducing still towith contact clay in the amount of The foregoing two runs, giving comparable results obtained by treating lubricating oil distillate from Texas coastal crude with aluminum chlorid in a single stage at high temperature and by treating the same stock in two stages, one at After again'separating. the sludge, theto sethigh temperature and one at lower temperature, are given in Table III, below:v

Table III Liugricatiilig oil disi. ate a uminum gg chlorid treatment distillate One stage Two stages Aluminum chlorid treatment:

First stage Chlorid used, lbs. per bbl 13 13 Chlorid used, percent .7

by weight 4 4 Treating temperature, F 470 470 Time of treating, a

hours .12 12 Second stage Chlorid used, lbs. per

bbl 19. 6 Chloridused, percent by weight 6 Treating temperature,

0.5 0.5 Temperature of reduction,

F 500 500 Distillate from reducing still,

percent 25. 6 33. 0 Yield of reduced oil, percent- 59. 8 40. 3 Tests:

- Gravity, A. P. I 20.3 22. 6 26.0

Viscosity, S. U. V.- 100 F 1462. 1038 v 789 80 75 74 20' 51 84 430 450 460 515 535 515 0 -10 +5 5. 25 8 2. 75 0. 29 0. 84 0.14

In the single stage treat at high temperature, shown in the second column of Table III, it will be noted that while the viscosity index was raised from 20 to 51, the carbon residue increased from It is generally recognized that the carbon residue test of a lubricating oil should be as low as possible. We treat at high temperature with a portion of our aluminum chlorid to get'an improvement in the viscosity index and then we treat with the remaining portion of aluminum chlorid at a lower temperature to reduce the carbon residue test and to attain further improvement in. viscosity index. This twostage treatment is not necessary with a parafllnic type oil as will be shown below. It seems to be peculiar to the naphthenic type only. It will-be' observed in the two-stage treatment shown in the third column of Table III that the viscosity index has been improved from 20 to 84, the latter index figure, obtained by our process in a product from Texas coastal crude, being somewhat higher than I the average for lubricating oils made from parafgallon of oil. The

sour oil was charged finic mid-continentcrudes. Conforming to the general rule already mentioned, the gravity of the treated oil is considerably lighter and the flash and fire tests are considerably higher than the original oil, for approximately the same viscosity at 210 F.

A reducedmid-continent crude of paraflinic type which had been treated with sulphuric acid and dewaxed, was further treated with 98% sulphuric acid in the amount of 42 pounds per barrel of oil, this being 13.1% by weigh Sludge re sulting from the treatment was settled and the to a reducing still together with contact clay in the amount of pound per oil was reduced at 500 F. with fire and bottom steam to a viscosity of 116 at 210 F.

Another lot of the same oil was treated with aluminum chlorid in the amount of 32 pounds per barrel of oil (10% by weight) at a temperature of 307 F. for twelve hours while stirring. The resulting sludge was separated from the supernatant oil, and the latter was charged to a reducing still together with pound of contact clay per gallon of oil. The oil was reduced at 500 F.,with fire and bottom steam to a viscosity of 88 at 210? F. The following table, relating to the two runs described in this and the next preceding paragraph, gives comparative results attained when using sulphuric acid and aluminum chlorid, separately, as treating agents.

Table IV Reduced crude-Mid-continent Acid Acid Acid dtreated:1 dtreated ewexe ewaxe :g U16? 1 then ur er a uminum dawned acid chlorid treated treated Acid treatment (98% sulfuric) Acid used, lbs. per bbl. 42 Acid used, byweight. l3. 1 Treating temperature, F 120-124 Aluminum chlorid treatment: Chlorid used, pounds per bbl 32 Chlorid used, by weight 10 Treating-temperature, F 307 Time of treating, hours... 12 Yield of treated oil, percent... 84. 4 Contact clay used, lbs. per

gal1 0.5 Temperature oi reduction, F 500 500 Distillate from reducing still,

percent l. 3 18.3 Yield of reduced oil, percent. 82. l 63. 2 'lests:

Gravity, A. P. I 22. 8 24. 8 .28. 2 Viscosity, S. U. V.

100 F 2356 2025 941 0 F 126 88 Viscosity index- 76 76 100 Flash, C O 510 515 495 Fire, C 0 F-- 590 600 575 Pour, F -e 0 +20 +30 Color, N. P. A 5.0 dd 5.0 2.0 Carbon residue, percent" l. 62 l. 14 0. 22

. used in the runs cited in I Yield oi treated oil, percent.

treatment raised the viscosity index to 100,

which is typical of oils derived from Pennsylvania crudes. At the sametime, we eiiected an extreme reduction in the carbon residue test when using a one-stage aluminum chlorid treatment.

Referring to the flash and fire tests of the aluminum chlorid treated material, it will be noted that these are somewhat lower than the original oil. But we would point out that the viscosity of the charge oil is 126 at 210 F. while the aluminum chlorid treated oil was reduced only to 88 viscosity. If the aluminum chlorid treated oil had been reduced to approximately 126 viscosity at 210 F., the flash and fire tests would have been considerably higher than those of the starting oil.

A reduced mid-continent crude, acid treated and dewaxedbut of higher viscosity than that Table IV, -was treated in one run with 98% sulphuric acid and in another run with aluminum chlorid. The details of treatment and the results attained are shown in Table V, below:

Table V Reduced crude-:Mid-continent Acid treatment (98% suliuric):

Acid used, lbs. per bbl..- Acid used, percent by weight Treating temperature, F Aluminum chlorid treatment: Cl'ijlglrid used, lbs. per Chlorid used, P rcent by weight Treating temperature, F Time oi treating, hours-.-

Contact clay used, lbs. per

ga Temperature of reduction,

Distillate from reducing still,

percent 0. 4 3i. 6 Yield of reduced oil, percent.. 77. 9 43. 4 22. l 23. 5 29. l

3669 2800 1097 162 97 74 77 102 555 545 555 640 630' 620 Pour, F +20 +25 +45 Color, N. P. A 5.5 dil. 6.25 1. 75 Carbon res ue, percent.- 2. l l. 49 0. 19

In the runs cited in Table V our aluminum chlorid treatment has changed the viscosityteniperature relationship of an oil from midcontinent crude to that typical of an oil from Pennsylvania crude. At the same time the carbon residue test has been reduced from 2.1% to 0.19%. It will be observed that sulphuric acid changed the viscosity index and carbon residue test only slightly.

A reducedWest Texas crude, from Reagan County, previously treated with sulphuric acid and dewaxed, was treated with aluminum chlorid. The details oi the treatment and the results attained are tabulated in Table VI.

Table VI Reduced West Texas crude-Reagan County Acid Acid treated, treated dewaxed and then dewaxed aluminum chlorid treated Aluminum chlorid treatment:

Chlorid used, pounds er barrel 22 Chlorid used, percent y weight 7 Treating temperature F 425 Time of treating, hours 12 Yield of treated oil, percent 84 Contact clay used, pounds er gallon 0. 5 Temperature of reduction, F- 500 Distillate from reducing still, perce 28. 1 Yield of reduced oil, percent 53.0 Tests:

Gravity, A. P. I.-. 30. 5 Viscosity, S. U. V.

100 F 1740 832 210 F 118 87 Viscosity index 92 109 Flash, 0. 0. 0. F 500 510 7 Fire, 0. O. 0., F 580 585 Pour, F +20 +30 Color, N. P. A dark 2.75 Carbon residue, percent l. 71 0. 12

West Texas crude from Reagan County yields lubricating oils with viscosity indexes similar to those from Pennsylvania crudes. With this particular crude, our process yields lubricating oils with viscosity indexes substantially higher than the average of lubricating oils from Pennsylvania crudes. The carbon residue test is reduced to a, negligible quantity by a single stage treatment.

A reduced Pennsylvania crude oil which had been dewaxed was treated with aluminum chlorid in the amount of 27.3 pounds per barrel of oil (9% by weight) at a temperature of 400 F. for 12 hours while stirring. Sludge resulting from the treatment was settled and withdrawn, and the treated oil was charged to a reducing still together with pound of contact clay per gallon of oil. The oil bottom steam at 500 F. to a viscosity of 78 at 210 F. Table VII below shows the results attained:

Table VII Reduced Pennsylvania crude Dewaxed, then alu- Dewaxed minum chlorid treated Aluminum Chlorid Treatment:

Chlorid used, lbs. per bbl 27.3 orid used, percent by weight 9. Treating temperature, 400 Time of treating, hours 12 Yield of treated oil, percent. 82. 3 Contact clay used, lbs per gel] 0, 5 Temperature of reduction. F 500 Distillate from reducing still, percent 18.0 Yield of reduced oil, percent 61.4 Tests:

Gravity, A. P. I 2519 31.0 Viscosity, S. U. V.

100 F 1544 590 210 F 116 78 Viscosity index 99 121 Flash, 0. 0. 0. F 485 425 Fire, 0. 0. 0., 560 500 Pour, F 0 Color. N. P. A 6.25 dil l. 75 Carbon residue, percen 1. 0.

It will be observed that by our process, we increased the viscosity index of this Pennsylvania oil from 99 to 121, and we lowered the carbon was there reduced with fire and 5 residue test from 1.62% to 0.13%. Such a prodnot could properly be characterized as Super- Pennsylvania in quality.

From the foregoing examples it is seen that the viscosity index of the oil was greatly improved in every instance. In the case of a lubricating distillate from Texas coastal crude an original viscosity index of 13 was brought up to 60 in one example, and, in another example, where a'twostage aluminum chlorid treatment was used, the viscosity index was increased from 20 to 84. With the mid-continent paraflin oils the viscosity index increased from 76 to 100 in one case and, in a second case, the viscosity index increased from 74 to 102. With a stock from a West Texas crude the viscosity index was raised from 92 to 109, and with a Pennsylvania stock the viscosity index was raised from 99 to 121.

With temperatures ranging from about 300 to 475, and with varying percentages of aluminum chlorid as high as 10 per cent, the viscosity indexes of lubricating 011 stocks can be greatly improved. A lubricating oil distillate from Texas coastal crude (naphthenic type-crude) can be treated to a viscosity index equal to that of a lubricating oil from the very best mid-continent crudes' (paraflin base), and a lubricating oil from a mid-continent crude can be treated to a viscosity index equal to a lubricating oil irom a Pennsylvania crude (paramnbase). Also, a Inbricating stock from a Pennsylvania crude can be treated to greatly improve its viscosity index, so that in its broader aspects my invention can be practiced with any improve its viscosity index. a

The oil resulting from the processes described is a good lubricating oil ready for use. It is, however, not essential that the fire and steam reduction be done in the presence of contact clay. I find it advantageous to do so; but that step can be omitted and the sour oil remaining after the aluminum chlorid treatment is in that event given neutralization treatment, and is then reduced by fire and steam to the desired viscosity. The treatment with aluminum chlorid improves the color to such a degree that filtration through fullers earth is not necessary, although it may be so filtered if desired. Should the wax content of the oil produced be considered excessive for any intended purpose it may be ventional dewaxing operation.

The described process is applicable to any lubricating oil stock, whether in the form of reduced, crude, or a distillate therefrom.

The optimum proportion of aluminum chloride for use in our processis an amount weighing in the neighborhood of 8% to 10% as much as the 011 being treated, and the optimum time of treatment from 8 hours to 12 hours. When treating at temperatures in the'neighborhoodof 300 F. this time can be greatly exceeded without disadvantage, but if this optimum time is/greatly exceeded at higher temperatures it x2Li ll result in undue loss of lubricating oil by co ersion into light viscous petroleum oil to subjected to a con- 5 6 desired effect in commercially justifiable degree. In applying our process to naphthenic type oils we find it especially advantageous to use twostage aluminum chlorid treatment, conducting the first stage treatment at a temperature within the approximate range 400 F. to 475 F., and conducting the second stage treatment at-a temperature within the approximate range 300 F. to 350 F. When treating at these temperatures, all other features of our process are practiced in accordance with our more detailed disclosure above.

What we claim is: 1. A process for improving the viscosity index of petroleum lubricating oil which comprises agitating a petroleum lubricating stock in the absence of any substantially lighter material with anhydrous aluminum chlorid for a number of hours at a temperature between 400 F. and 475 F.; separating the so treated oil from any sludge which may result from the aluminum chlorid treatment; subjecting the separated oil to a second treatment with anhydrous aluminum chlorid at a temperature between 300 F. and 350 R;

separating the twice treated oil 'from anysludge which may result from the aluminum chlorid treatment; and distilling ofi any low boiling product of the treatment.

2. A process for improving the viscosity index 5 of petroleum oil which comprises treating a petroleum lubricating stock in the absence of any substantially lighter material and in the absence of added HCl with anhydrous aluminum chlorid for from 4 to 12 hours at a temperature between 10 425 F. and 500 F., said treatment resulting in the conversion of a substantial part of the stock into lower boiling components and in a lowering of the viscosity of the material under treatment; separating the so treated stock from any sludge which, may result from the aluminum chlorid treatment; and distilling the so separated oil to remove the lower boiling components resulting from the treatment and so securing a residue of lubricating oil of higher viscosity index than the 20 untreated oil. a

ALMER M. McAFEE.

LUCIEN 0. CROCKETT. 

